Lubricant Providing Improved Cleanliness For Two-Stroke Cycle Engines

ABSTRACT

A lubricant composition comprising an oil of lubricating viscosity, 0.1 to 2 percent by weight of a Mannich dispersant, and 0.1 to 2 percent by weight of a succinimide dispersant, wherein the succinimide dispersant provides at least about 40 parts per million by weight of nitrogen atoms to the lubricant composition, provides cleanliness to a two-stroke cycle engine.

BACKGROUND OF THE INVENTION

The disclosed technology relates to an engine lubricant, particularlyfor two-stroke cycle engines.

Two-stroke cycle engines are widely used for portable power equipmentand also represent an important portion of the engines used intransportation, particularly in the developing regions of the world. Thelubricants required for the operation of two-stroke cycle engines are,in some designs, mixed with the liquid fuel, and this fuel-lubricantmixture is typically passed through the crankcase and, ultimately, tothe combustion chambers, where the entire fuel-lubricant composition isburned. It is important, in such engines, to provide a lubricantcomposition which maintains suitable properties of lubricity andcleanliness. Problems with cleanliness can be observed as deposit orvarnish formation within the engine in such areas as the piston skirt,the ring area of the piston, or the crankcase. It is desired to find aneconomical lubricant additive package that provides good cleanliness toa two-stroke cycle engine.

U.S. Publication 2011-0030637, Dohner et al., Feb. 10, 2011 (previouslypublished as WO2009/126381, Oct. 15, 2009), discloses a lubricantcomprising, among other components, about 3 to about 30 percent byweight of a nitrogen-containing dispersant bearing a hydrocarbyl groupof at least 26 carbon atoms and having a nitrogen content of at least 3percent by weight, wherein the nitrogen content of the lubricant is atleast about 0.2 percent by weight. The dispersant may be a succinimidedispersant. The lubricant may further comprise about 1.1 to about 15percent by weight of a Mannich dispersant.

U.S. Pat. No. 7,900,590, Cleveland et al., Mar. 8, 2011 (previouslypublished as US 2005/0139174, Jun. 30, 2005) discloses methods andlubricant and fuel compositions for two-stroke engine containing powervalves. A lubricant composition comprises, among other components, (A)an oil of lubricating viscosity and (B) an additive composition thatcomprises (1) a reaction product of a fatty hydrocarbyl-substitutedmonocarboxylic acylating and a (select) reactive nitrogen-containingcompound; and (2) a member selected from the group consisting of (a) ahydrocarbyl-substituted aminophenol; (b) a Mannich reaction product of ahydrocarbyl-substituted phenol, an aldehyde, and an amine; (c) areaction product of a hydrocarbyl-substituted polycarboxylic acylatingagent and a polyamine; and (d) a mixture thereof. Thehydrocarbyl-substituted polycarboxylic acylating agent can be apolyisobutenylsuccinic anhydride.

U.S. Pat. No. 7,795,192, Petric et al., Sep. 14, 2010 (previouslypublished as US 2005-013856, Jun. 16, 2005), discloses a lubricantcomposition suitable for lubricating a direct fuel injection two-strokeengine, comprising, among other components, a condensation product of afatty hydrocarbyl monocarboxylic acid with a polyethylene polyamine, anda Mannich dispersant, being the reaction product of apolybutene-substituted phenol, formaldehyde, and ethylenediamine ordimethylamine. The lubricant may further comprise an additionaldispersant which may be, among others, a mono-succinimide dispersant.

U.S. Publication 2008-0009428, Svarcas et al., Jan. 10, 2008, disclosesa lubricant composition suitable for lubricating a two stroke enginecomprising an oil of lubricating viscosity, a synthetic ester, anormally liquid solvent, a Mannich dispersant, and a condensationproduct of a fatty acid having about 12 to about 24 carbon atoms with apolyamine. In a comparative example, a commercial two-cycle oilcomprises, among other components, a fatty acid imidazole dispersant,and a succinimide dispersant.

SUMMARY OF THE INVENTION

The disclosed technology provides a lubricant composition comprising:(a) an oil of lubricating viscosity; (b) 0.1 to 2 percent by weight of aMannich dispersant; and (c) 0.2 to 2 percent by weight of a succinimidedispersant; wherein the succinimide dispersant provides at least about40 parts per million by weight of nitrogen atoms to the lubricantcomposition. In one embodiment, the lubricant composition furthercomprises (d) a metal-containing detergent.

The disclosed technology also provides a method of lubricating aninternal combustion engine, such as a two-stroke cycle engine,comprising supplying thereto the lubricant composition.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

One component of the disclosed technology is an oil of lubricatingviscosity, also referred to as a base oil. The base oil may be selectedfrom any of the base oils in Groups I-V of the American PetroleumInstitute (API) Base Oil Interchangeability Guidelines, namely

Base Oil Category Sulfur (%) Saturates(%) Viscosity Index Group I >0.03and/or <90 80 to 120 Group II ≦0.03 and ≧90 80 to 120 Group III ≦0.03and ≧90 >120 Group IV All polyalphaolefins (PAOs) Group V All others notincluded in Groups I, II, III or IVGroups I, II and III are mineral oil base stocks. The oil of lubricatingviscosity can include natural or synthetic oils and mixtures thereof.Mixture of mineral oil and synthetic oils, e.g., polyalphaolefin oilsand/or polyester oils, may be used. In some embodiments of the presentinvention, the oil will be a mineral oil, that is, Group I, II, or III,and in some embodiments it will be a Group II oil or a Group III oil.

Natural oils include animal oils and vegetable oils (e.g. vegetable acidesters) as well as mineral lubricating oils such as liquid petroleumoils and solvent-treated or acid treated mineral lubricating oils of theparaffinic, naphthenic or mixed paraffinic-naphthenic types.Hydrotreated or hydrocracked oils are also useful oils of lubricatingviscosity. Oils of lubricating viscosity derived from coal or shale arealso useful.

Synthetic oils include hydrocarbon oils and halosubstituted hydrocarbonoils such as polymerized and interpolymerized olefins and mixturesthereof, alkylbenzenes, polyphenyl, alkylated diphenyl ethers, andalkylated diphenyl sulfides and their derivatives, analogs andhomologues thereof. Alkylene oxide polymers and interpolymers andderivatives thereof, and those where terminal hydroxyl groups have beenmodified by, e.g., esterification or etherification, are other classesof synthetic lubricating oils. Other suitable synthetic lubricating oilscomprise esters of dicarboxylic acids and those made from C₅ to C₁₂monocarboxylic acids and polyols or polyol ethers. Other syntheticlubricating oils include liquid esters of phosphorus-containing acids,polymeric tetrahydrofurans, silicon-based oils such as poly-alkyl-,polyaryl-, polyalkoxy-, or polyaryloxy-siloxane oils, and silicate oils.

Other synthetic oils include those produced by Fischer-Tropschreactions, typically hydroisomerized Fischer-Tropsch hydrocarbons orwaxes. In one embodiment oils may be prepared by a Fischer-Tropschgas-to-liquid synthetic procedure as well as other gas-to-liquid oils.

Unrefined, refined and rerefined oils, either natural or synthetic (aswell as mixtures thereof) of the types disclosed hereinabove can beused. Unrefined oils are those obtained directly from a natural orsynthetic source without further purification treatment. Refined oilsare similar to the unrefined oils except they have been further treatedin one or more purification steps to improve one or more properties.Rerefined oils are obtained by processes similar to those used to obtainrefined oils applied to refined oils which have been already used inservice. Rerefined oils often are additionally processed to remove spentadditives and oil breakdown products.

Another components that may be considered a part of the oil oflubricating viscosity includes bright stock (a high viscosity mineraloil fraction), which may be typically present, if desired, in amounts of1 to 5 or 1.5 to 3 percent by weight.

The amount of oil of lubricating viscosity in a fully formulatedlubricant of the disclosed technology (including the diluent or carrieroils present in the additional components) will typically be 20 to 60percent by weight, or 25 to 55 percent, or 30 to 50 percent by weight.

The lubricant will also include a Mannich dispersant and a succinimidedispersant. Dispersants in general are well known in the field oflubricants and include primarily what is known as ashless dispersantsand polymeric dispersants. Ashless dispersants are so-called because, assupplied, they do not contain metal and thus do not normally contributeto sulfated ash when added to a lubricant. However they may, of course,interact with ambient metals once they are added to a lubricant whichincludes metal-containing species. Ashless dispersants are characterizedby a polar group attached to a relatively high molecular weighthydrocarbon chain.

One component of the present technology is a Mannich dispersant,sometimes referred to as a Mannich base dispersant. A Mannich dispersantis a reaction product of a hydrocarbyl-substituted phenol, an aldehyde,and an amine or ammonia. The hydrocarbyl substituent of thehydrocarbyl-substituted phenol can have 10 to 400 carbon atoms, inanother instance 30 to 180 carbon atoms, and in a further instance 10 or40 to 110 carbon atoms. This hydrocarbyl substituent can be derived froman olefin or a polyolefin. Useful olefins include alpha-olefins, such as1-decene, which are commercially available.

The polyolefins which can form the hydrocarbyl substituent can beprepared, for instance, by polymerizing olefin monomers by well-knownpolymerization methods and are also commercially available. The olefinmonomers include monoolefins, including monoolefins having 2 to 10carbon atoms such as ethylene, propylene, 1-butene, isobutylene, and1-decene. An especially useful monoolefin source is a C4 refinery streamhaving a 35 to 75 weight percent butene content and a 30 to 60 weightpercent isobutene content. Useful olefin monomers also include diolefinssuch as isoprene and 1,3-butadiene. Olefin monomers can also includemixtures of two or more monoolefins, of two or more diolefins, or of oneor more monoolefins and one or more diolefins. Useful polyolefinsinclude polyisobutylenes having a number average molecular weight of 140to 5000, in another instance of 400 to 2500, and in a further instanceof 140 or 500 to 1500. The polyisobutylene can have a vinylidene doublebond content of 5 to 69%, in a second instance of 50 to 69%, and in athird instance of 50 to 95%. The polyolefin can be a homopolymerprepared from a single olefin monomer or a copolymer prepared from amixture of two or more olefin monomers. Also possible as the hydrocarbylsubstituent source are mixtures of two or more homopolymers, two or morecopolymers, or one or more homopolymers and one or more copolymers. Theforegoing description of suitable hydrocarbyl groups or polyolefingroups is also applicable to the hydrocarbyl substituent of thesuccinimide dispersant, described in detail below.

The hydrocarbyl-substituted phenol which is used to prepare the Mannichdispersant can be prepared by alkylating phenol with an olefin orpolyolefin described above, such as a polyisobutylene or polypropylene,using well-known alkylation methods.

The aldehyde used to form the Mannich dispersant can have 1 to 10 carbonatoms, and is generally formaldehyde or a reactive equivalent thereofsuch as formalin or paraformaldehyde.

The amine used to form the Mannich dispersant can be a monoamine or apolyamine, including those materials described above for the succinimidedispersants, including alkanolamines having one or more hydroxyl groups.Useful amines include ethanolamine, diethanolamine, methylamine,dimethylamine, ethylenediamine, dimethylaminopropylamine,diethylenetriamine and 2-(2-aminoethylamino)ethanol. The Mannichdispersant can be prepared by reacting a hydrocarbyl-substituted phenol,an aldehyde, and an amine as described in U.S. Pat. No. 5,697,988. Inone embodiment, the Mannich reaction product is prepared from analkylphenol derived from a polyisobutylene, formaldehyde, and an aminethat is a primary monoamine, a secondary monoamine, or analkylenediamine, in particular, ethylenediamine or dimethylamine. In oneembodiment, the alkylphenol may be prepared from a high-vinylidenepolyisobutene, having, e.g., greater than 50, greater than 70 or greaterthan 75 percent terminal vinylidene groups (i.e., such percentage ofpolyisobutylene molecules having vinylidene end groups; that is, molepercentage of polyisobutylene molecules having a terminal vinylidenegroup.) The foregoing description of the amine is also applicable to thedescription of the amine used in preparing the succinimide dispersant,described below.

In one embodiment the Mannich dispersant comprises the reaction productof a hydrocarbyl-substituted phenol, formaldehyde or a reactiveequivalent of formaldehyde, and a primary or secondary amine. In oneembodiment the Mannich dispersant comprises the reaction product of apolyisobutene-substituted phenol, formaldehyde or a reactive equivalentof formaldehyde, and dimethylamine.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude hydrocarbon substituents, including aliphatic, alicyclic, andaromatic substituents; substituted hydrocarbon substituents, that is,substituents containing non-hydrocarbon groups which, in the context ofthis invention, do not alter the predominantly hydrocarbon nature of thesubstituent; and hetero substituents, that is, substituents whichsimilarly have a predominantly hydrocarbon character but contain otherthan carbon in a ring or chain. A more detailed definition of the term“hydrocarbyl substituent” or “hydrocarbyl group” is found in paragraphs[0137] to [0141] of published application US 2010-0197536.

The amount of the Mannich dispersant will typically be 0.1 to 2 percentby weight of the lubricant composition. In other embodiments it may bepresent at 0.15 to 1.5 percent, or 0.2 to 1.05 percent, or 0.2 to 1percent, or 0.3 to 0.6 percent by weight.

A second type of dispersant that will be present in the disclosedcompositions is a succinimide dispersant. In one embodiment, thesuccinimide dispersant is a condensation product ofhydrocarbyl-substituted succinic anhydride or a reactive equivalentthereof (e.g., an anhydride, ester, or acid halide), with a polyethylenepolyamine. Succinimide dispersants may generally be viewed as comprisinga variety of chemical structures including typically

where each R¹ is independently an alkyl group, frequently apolyisobutylene group with a molecular weight (M_(n)) of 500-5000 basedon the polyisobutylene precursor, and R² are alkylene groups, commonlyethylene (C₂H₄) groups. Such molecules are commonly derived fromreaction of an alkenyl acylating agent with a polyamine, and a widevariety of linkages between the two moieties is possible beside thesimple imide structure shown above, including a variety of amides andquaternary ammonium salts. In the above structure, the amine portion isshown as an alkylene polyamine, although other aliphatic and aromaticmono- and polyamines may also be used. Also, a variety of modes oflinkage of the R¹ groups onto the imide structure are possible,including various cyclic linkages. The ratio of the carbonyl groups ofthe acylating agent to the nitrogen atoms of the amine may be 1:0.5 to1:3, and in other instances 1:1 to 1:2.75 or 1:1.5 to 1:2.5. Succinimidedispersants are more fully described in U.S. Pat. Nos. 4,234,435 and3,172,892 and in EP 0355895.

Succinimide dispersants may also be described as being prepared fromhydrocarbyl-substituted succinic acylating agent which are, in turn,prepared by the so-called “chlorine” route or by the so-called “thermal”or “direct alkylation” route. These routes are described in detail inpublished application US 2005-0202981, paragraphs 0014 through 0017. Adirect alkylation or low-chlorine route is also described in U.S. Pat.No. 6,077,909; refer to column 6 line 13 through col. 7 line 62 andcolumn 9 lines 10 through col. 10 line 11. Illustrative thermal ordirect alkylation processes involve heating a polyolefin, typically at180 to 250° C., with maleic anhydride under an inert atmosphere. Eitherreactant may be in excess. If the maleic anhydride is present in excess,the excess may be removed after reaction by distillation. Thesereactions may employ, as the polyolefin, high vinylidenepolyisobutylene, that is, having greater than 50, 70, or 75% terminalvinylidene groups (α and β isomers). In certain embodiments, thesuccinimide dispersant may be prepared by the direct alkylation route.In other embodiments it may comprise a mixture of direct alkylation andchlorine-route dispersants.

The succinimide dispersant will be one which is capable of providing arelatively large quantity of nitrogen to the lubricant. The nitrogenwill be nitrogen atoms that are a part of the amine component or thecondensed amide or imide groups of the dispersant. That is, it willimpart at least 40 parts per million by weight of nitrogen to thelubricant, and in some embodiments at least 70 or 100 or 130 or 150parts per million, and up to, for example, 1000 or 900 or 800 or 600parts per million. These amounts will be determined by both the amountof the succinimide dispersant in the lubricant formulation and theamount of nitrogen within the given dispersant. Thus, certain of thesuccinimide dispersants of the present technology are comparatively highin nitrogen content, i.e., at least 3 percent or at least 4 percent orat least 4.4 percent by weight, and up to 6 or 5.5 or 5 percent.

Such high nitrogen dispersants are, in certain embodiments,characterized as having a high TBN, total base number (ASTM D 974), dueto the presence of basic amine functionality. The present succinimidedispersant may thus have a TBN of at least 90 or 100 or 110 and up to,for instance, 160 or 140 or 120. Other suitable TBN ranges may be 60 to160 or 70 to 140 or 80 to 120. Such values are to be calculated on thebasis of an oil-free dispersant, as will be evident to the skilledperson. In certain applications, the succinimide dispersant may beborated.

The amount of the succinimide dispersant will typically be 0.1 to 2percent by weight of the lubricant composition. In other embodiments itmay be present at 0.15 to 1.5 percent, or 0.2 to 1 percent, or 0.3 to0.6 percent by weight. The relative amounts of the Mannich dispersantand the succinimide dispersant, expressed as a weight ratio, may be80:20 to 20:80 or alternatively 70:30 to 30:70 or 65:35 to 45:55. Thetotal amount of the Mannich dispersant and the succinimide dispersant,and optionally any other nitrogen-containing dispersants that may bepresent, may be 0.2 to 4 percent by weight, or 0.3 to 3 percent, or 0.4to 2 percent.

Other dispersants may also be present, if desired. They may be lowernitrogen-content dispersants than the above-described succinimidedispersant, or they may have shorter or longer hydrocarbyl chains, orthey may have other functional groups. One such dispersant may be acondensation product of a fatty hydrocarbyl monocarboxylic acylatingagent, such as a fatty acid, with an amine. The fatty acid may contain10 to 26 carbon atoms (e.g., 12 to 24 or 14 to 20 or 16 to 18). Anexample is isostearic acid. The amine may be a polyethylene polyamine asdescribed above. The condensation product may be an amide or animidazoline. Other dispersants include high molecular weight esters.These materials are similar to the above-described succinimides exceptthat they may be seen as having been prepared by reaction of ahydrocarbyl acylating agent and a polyhydric aliphatic alcohol such asglycerol, pentaerythritol, or sorbitol. Other dispersants includepolymeric dispersant additives, also referred to as dispersant viscositymodifiers, which are generally hydrocarbon-based polymers containingpolar functionality to impart dispersancy characteristics to thepolymer.

Either one or both or all of the dispersants may be post-treated withany of a variety of agents to impart desirable properties thereto, whileretaining, in some embodiments, a relatively high TBN for thesuccinimide dispersant. Such post-treatment includes reaction with urea,thiourea, dimercaptothiadiazoles, carbon disulfide, aldehydes, ketones,carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles,epoxides, boron compounds such as boric acid, phosphorus compounds, ormixtures thereof. References detailing such treatment are listed in U.S.Pat. No. 4,654,403.

Other materials may also be present in the lubricants described herein,and in particular those materials which are desirable to provide alubricant for a two-stroke cycle engine. One such material is a solvent,which may be used to aid in the solubility of the additives in thelubricant or in the fuel with which it is conventionally to be mixed orto adjust the viscosity parameters of the lubricant. Typically such amaterial is a combustible solvent (other than oil of lubricatingviscosity, described above), having a flash point of less than about105° C., in which the remaining components of the lubricant are soluble.The solvent is typically a hydrocarbonaceous solvent, that is, one whichexhibits principally hydrocarbon character, even though relatively smallnumbers of heteroatoms may be present in the molecule. The solvent maybe a hydrocarbon and may have predominantly non-aromatic (e.g., alkane)character. The solvent may thus comprises less than 20 percent by weightaromatic components and may be substantially free from polynucleararomatic components. A particularly suitable solvent is kerosene, whichis a non-aromatic petroleum distillate having a boiling range of180-300° C. Another useful solvent is Stoddard solvent, which has aboiling range of 154-202° C.

The solvent is characterized by a kinematic viscosity of less than 5 mm²s⁻¹ (cSt) at 100° C., such as less than 2.0 or 1.5 or 1.0 mm2 s−1. Thus,solvents are of lower viscosity than the oils of lubricating viscosity,which, accordingly, may have a kinematic viscosity of at least 1.0 or1.5 or 2.0 or 5 mm⁻ s⁻¹ at 100° C.

The amount of the solvent, if it is present, may be at least 5 percentby weight of the lubricant, or at least 10 percent, up to 50 or 40 or 30percent. Suitable ranges may include combinations of the above values,or 15 to 30 percent by weight.

The lubricant composition may also contain a polymer such aspolyisobutene, or, more generally, an olefin polymer. Olefin polymersare well known as additives for two-stroke cycle engines. Generally theyare relatively low molecular weight materials, having a molecular weight(number average) of 5000 or less, such as 500 to 3000 or 1000 to 2500.Occasionally, however, higher molecular weight olefin polymers have beenused in two-cycle lubricants; see, for example, U.S. Pat. No. 5,741,764,Patel et al., Apr. 21, 1991. Such polymers may be hydrogenated to removemost or all of any remaining ethylenic unsaturation. If an olefincopolymer, such as a low molecular weight polyisobutylene is present, itmay be present in an amount of up to 50 percent, such as 10 to 50percent by weight or 15 to 45 percent or 20 to 40 percent or 25 to35percent by weight.

Another material which may be present is a hydrocarbyl-substitutedphenol. This may be a similar material to that used in the preparationof the Mannich dispersant, above, and its description as recited therewill be applicable for this component as well. In one embodiment, thehydrocarbyl-substituted phenol may be a polyisobutylene-substitutedphenol, and the polyisobutylene group may have a number averagemolecular weight of 300 to 3000 or 500 to 2000 or 750 to 1600 or about1000. It is believed that the presence of a hydrocarbyl-substitutedphenol may provide some antioxidant performance to the lubricant. Thehydrocarbyl phenol, if it is present, may be present, in an amount of upto 10 percent, such as 1 to 5 percent or 2 to 4 percent or 2.5 to 3.5percent by weight.

The lubricant composition may also contain a detergent such as ametal-containing detergent. Detergents are often overbased materials,otherwise referred to as overbased or superbased salts. These aregenerally single phase, homogeneous Newtonian systems characterized by ametal content in excess of that which would be present forneutralization according to the stoichiometry of the metal and theparticular acidic organic compound reacted with the metal. The overbasedmaterials are prepared by reacting an acidic material (typically aninorganic acid or lower carboxylic acid, preferably carbon dioxide) witha mixture comprising an acidic organic compound, a reaction mediumcomprising at least one inert, organic solvent (e.g., mineral oil,naphtha, toluene, xylene) for said acidic organic material, astoichiometric excess of a metal base, and a promoter such as a phenolor alcohol.

The acidic organic material will normally have a sufficient number ofcarbon atoms to provide a degree of solubility in oil. The amount ofexcess metal is commonly expressed in terms of metal ratio. The term“metal ratio” is the ratio of the total equivalents of the metal to theequivalents of the acidic organic compound. A neutral metal salt has ametal ratio of one. A salt having 4.5 times as much metal as present ina normal salt will have metal excess of 3.5 equivalents, or a ratio of4.5.

Such overbased materials are well known to those skilled in the art.Patents describing techniques for making basic salts of alkylaromaticsulfonic acids, carboxylic acids, phenols, phosphonic acids, andmixtures of any two or more of these include U.S. Pat. Nos. 2,501,731;2,616,905; 2,616,911; 2,616,925; 2,777,874; 3,256,186; 3,384,585;3,365,396; 3,320,162; 3,318,809; 3,488,284; and 3,629,109. Yet otherdetergents are referred to as salixarate detergents. These includeoverbased materials prepared from salicylic acid (which may beunsubstituted) with a hydrocarbyl-substituted phenol, such entitiesbeing linked through —CH2- or other alkylene bridges. It is believedthat the salixarate derivatives have a predominantly linear, rather thanmacrocyclic, structure, although both structures are intended to beencompassed by the term “salixarate.” Salixarate derivatives and methodsof their preparation are described in greater detail in U.S. Pat. No.6,200,936 and PCT Publication WO 01/56968.

In certain embodiments the detergent may be an overbased sulfonate,phenate, salicylate, or salixarate detergent. In certain embodiments itmay comprise an overbased calcium phenate detergent. The phenols usefulin making phenate detergents can be represented by (R¹)_(a)—Ar—(OH)_(b),where R¹ is an aliphatic hydrocarbyl group of 4 to 400 or 6 to 80 or 6to 30 or 8 to 25 or 8 to 15 carbon atoms; Ar is an aromatic group suchas benzene, toluene or naphthalene; a and b are each at least one, thesum of a and b being up to the number of displaceable hydrogens on thearomatic nucleus of Ar, such as 1 to 4 or 1 to 2. There is typically anaverage of at least 8 aliphatic carbon atoms provided by the R¹ groupsfor each phenol compound. Phenate detergents are also sometimes providedas sulfur-bridged species.

While the metal salt of the phenate detergent is typically calcium, themetal compounds useful in making the basic metal salts are moregenerally any Group 1 or Group 2 metal compounds (CAS version of thePeriodic Table of the Elements). Examples include alkali metals such assodium, potassium, lithium, copper, magnesium, calcium, barium, zinc,and cadmium. In one embodiment the metals are sodium, magnesium, orcalcium. The anionic portion of the basic metal compound can behydroxide, oxide, carbonate, borate, or nitrate.

In certain embodiments the metal-containing detergent contributes atleast about 0.1 total base number, or at least 0.3 or 0.4 or 0.6 TBN tothe lubricant composition, and in some embodiments up to 3 or 2 or 1TBN. The amount of the metal-containing detergent, if present, may incertain embodiments be up to 3 percent, e.g., 0.1 to 3 percent or 0.2 to2 percent or 0.25 to 1 percent or 0.3 to 0.6 percent by weight. In otherembodiments, the metal-containing detergent may be present in an amountto deliver at least 0.01 percent sulfated ash to the composition. Thedetergent may be present in an amount to deliver 0.01 to 0.12 percentsulfated ash or, alternatively, 0.05 to 0.1 percent, or even 0.06 to0.09 percent. In certain embodiments, the present lubricant is not anash-free lubricant; that is, it may be an ash-containing detergent,containing 0.01 to 0.12 percent sulfated ash or, alternatively, 0.05 to0.1 percent, or even 0.06 to 0.09 percent, which ash may be provided bythe metal-containing detergent or detergents or in whole or in part fromother sources such as zinc salts (e.g., zinc dialkyldithiophosphates),molybdenum compounds, or titanium compounds.

Another material which may be present in the lubricant is anantioxidant. Antioxidants encompass phenolic antioxidants, which may behindered phenolic antioxidants, one or both ortho positions on aphenolic ring being occupied by bulky groups such as t-butyl. The paraposition may also be occupied by a hydrocarbyl group or a group bridgingtwo aromatic rings. In certain embodiments the para position is occupiedby an ester-containing group, such as, for example, an antioxidant ofthe formula

wherein R³ is a hydrocarbyl group such as an alkyl group containing,e.g., 1 to 18 or 2 to 12 or 2 to 8 or 2 to 6 carbon atoms; and t-alkylcan be t-butyl. Such antioxidants are described in greater detail inU.S. Pat. No. 6,559,105.

Antioxidants also include aromatic amines. In one embodiment, anaromatic amine antioxidant can comprise an alkylated diphenylamine suchas nonylated diphenylamine or a mixture of a di-nonylated and amono-nonylated diphenylamine.

Antioxidants also include sulfurized olefins such as mono- or disulfidesor mixtures thereof. These materials generally have sulfide linkages of1 to 10 sulfur atoms, e.g., 1 to 4, or 1 or 2. Materials which can besulfurized to form the sulfurized organic compositions of the presentinvention include oils, fatty acids and esters, olefins and polyolefinsmade thereof, terpenes, or Diels-Alder adducts. Details of methods ofpreparing some such sulfurized materials can be found in U.S. Pat. Nos.3,471,404 and 4,191,659.

Molybdenum compounds can also serve as antioxidants, and these materialscan also serve in various other functions, such as antiwear agents orfriction modifiers. U.S. Pat. No. 4,285,822 discloses lubricating oilcompositions containing a molybdenum- and sulfur-containing compositionprepared by combining a polar solvent, an acidic molybdenum compound andan oil-soluble basic nitrogen compound to form a molybdenum-containingcomplex and contacting the complex with carbon disulfide to form themolybdenum- and sulfur-containing composition.

Typical amounts of antioxidants will, of course, depend on the specificantioxidant and its individual effectiveness, but illustrative totalamounts can be 0.005 to 5 percent by weight or 0.007 to 1 percent or0.01 to 0.5 percent of 0.01 to 0.1 percent.

Yet another material that may optionally be present, or which may beabsent, is a metal salt of a phosphorus acid. Metal salts of the formula

[(R⁸O)(R⁹O)P(═S)—S]_(n)-M

where R⁸ and R⁹ are independently hydrocarbyl groups containing 3 to 30carbon atoms, are readily obtainable by heating phosphorus pentasulfide(P₂S₅) and an alcohol or phenol to form an O,O-dihydrocarbylphosphorodithioic acid. The alcohol which reacts to provide the R⁸ andR⁹ groups may be a mixture of alcohols, for instance, a mixture ofisopropanol and 4-methyl-2-pentanol, and in some embodiments a mixtureof a secondary alcohol and a primary alcohol, such as isopropanol and2-ethylhexanol. The resulting acid may be reacted with a basic metalcompound to form the salt. The metal M, having a valence n, generally isaluminum, tin, manganese, cobalt, nickel, zinc, or copper, and in manycases, zinc, to form zinc dialkyldithiophosphates (“ZDDP”). Suchmaterials are well known and readily available to those skilled in theart of lubricant formulation. Suitable variations to provide goodphosphorus retention in an engine are disclosed, for instance, in USpublished application 2008-0015129, see, e.g., claims. In certainembodiments, the lubricant formulation may be free from ZDDP or maycontain only a low amount of one or more ZDDPs, such as to provide 0 to0.05, or 0.001 to 0.02, or 0.001 to 0.005, or 0.005 to 0.01 weightpercent phosphorus to the composition, and in one embodiment thelubricant formulation may contain the aforementioned amounts ofphosphorus from all sources, total.

Other conventional components may also be present, including pour pointdepressants; friction modifiers such as fatty esters; viscosity indexmodifiers; metal deactivators; rust inhibitors, corrosion inhibitors,high pressure additives, anti-wear additives, and antifoam agents. Anyof these materials can be present or can be eliminated, if desired.

The components of the present invention can be prepared by mixing theindicated components directly, or by preparing one or more of thecomponents in the form of a concentrate, to which other components (suchas oil or solvent) can subsequently be added.

The present lubricant may be supplied to an engine in any of a varietyof ways, depending at least in part on the design of the engine. It maybe supplied from a sump, in which case the optional volatile solventswill likely not be present. This arrangement would be more likely usedin engines which are not designed to consume the lubricant in thecombustion chamber. Many two-stroke cycle engines, however, are notsump-lubricated, and for them, the lubricant may be supplied along withthe fuel, either by injection into the fuel stream or by premixing thelubricant into the bulk fuel.

The fuel into which the lubricant for a two-cycle engine is mixed iscommonly, but not necessarily, gasoline. Other possible liquid fuelsincluded gasoline-alcohol mixtures (“gasohol”) having 5%, 10%, or alarger percentage of ethanol, including 85% (“E-85”). The lubricant maybe blended into the liquid fuel in an amount or ratio of 1:200 to 1:25by weight, or 1:60 to 1:40, or about 1:50 (e.g., about 2% lubricant).

The lubricant of the present technology may be profitably employed in atwo-stroke cycle engine. Such engines are commonly used in lawn andgarden equipment, portable contractor equipment such as pumps andelectrical generators, low-cost transportation vehicles, such as mopeds,as well as commercial and recreational vehicles including motorcycles,outboard engines (for boats and marine vehicles), snowmobiles, andpersonal watercraft vehicles. In some larger recreational applicationsas in outboard engines, engines with a displacement of 2,000 to 3,000cm³ generate approximately 150 kW (201 hp). 2-stroke cycle engines canalso be found in very small applications, such as in power tools likeweed trimmers or chain saws. These smaller engines typically output 1-5kW and may have a cylinder displacement of 20 to 80 cm³. In someembodiments, therefore, the engines may have a power output of less than150 kW, such as less than 100 or less than 50 or less than 20 kW; or 0.1to 15 kW or 0.5 to 10 kW or 1-5 kW, and optionally a cylinderdisplacement of 10 to 300 cm³, or 15-100 or 20-80 cm³.

The amount of each chemical component described is presented exclusiveof any solvent or diluent oil, which may be customarily present in thecommercial material, that is, on an active chemical basis, unlessotherwise indicated. However, unless otherwise indicated, each chemicalor composition referred to herein should be interpreted as being acommercial grade material which may contain the isomers, by-products,derivatives, and other such materials which are normally understood tobe present in the commercial grade.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a detergent) can migrate to other acidic oranionic sites of other molecules. The products formed thereby, includingthe products formed upon employing the composition of the presentinvention in its intended use, may not be susceptible of easydescription. Nevertheless, all such modifications and reaction productsare included within the scope of the present invention; the presentinvention encompasses the composition prepared by admixing thecomponents described above.

EXAMPLES

A series of lubricant compositions is tested in an SRM-265 two-strokecycle string trimmer engine, 25.4 cm³ engine displacement. The test isconducted for 50 hours or until engine seizure occurs, running theengine on a gasoline-lubricant mixture. The test consists of two stages,a full throttle portion and an idle portion. The engine is operated atthe full throttle condition for 2 minutes and 15 seconds. The engine isoperated at the idle condition for 15 seconds. These two cycles arerepeated for a total duration of 50 hours without interruption. At theend of the test, the engine is disassembled and inspected for varnishdeposits and port blocking The lubricants and the piston skirt varnishratings are reported in the table below. ASTM merit scale ratings areused to evaluate engine parts with a rating of 10 representing a cleanpart and lower numbers representing more severe degrees of varnish downto the most severe which has a merit rating of 1.

Amounts, % by weight Ex 1* Ex 2* Ex 3 Ex 4* Mineral oil: Balance to =100% Polyisobutene 27.7 27.7 27.7 27.7 Solvent 17.7 17.3 17.3 17.3Commercial viscosity index improver^(a) 0.21 0.21 0.21 0.21Antioxidant^(b) 0.01 0.01 0.01 0.01 Polyolefin-substituted phenol 3.03.0 3.0 3.0 Overbased Ca phenate detergent 0.35 0.35 0.35 0.35 Mannichdispersant^(c) — — 1.00 2.00 Succinimide dispersant^(d) — 1.73 0.86 —Piston skirt varnish rating 3.8 4.8 7.4 5.2 *A reference or comparativeexample. ^(a)Viscoplex ™ 1-3003 from Rohmax, as received, including anyoil ^(b)Ethanox ™, from Albemarle ^(c)product of polyisobutylene phenol,formaldehyde, and dimethylamine; includes 10-11% heavy aromatic solvent.^(d)4.7% N content

The results show markedly improved piston skirt varnish with Example 3of the present invention, compared with the reference examples havingapproximately the same total amount of dispersants.

The formulations below are subjected to a low temperature detergencytest. The test lubricant is used to lubricate a Husqvarna HVA 232E-Tech™ Scrub Cutter engine, a two-stroke cycle engine. After a 15minute breaking in phase, the carburetor H-needle is set to provide 3%CO at 8400 r.p.m., steady state conditions. The test cycle comprises 2seconds at full throttle followed by 3 seconds at idle, continuing for36,000 cycles over 50 hours. The only load is the inertia from the grasscutter. The L-needle is set to give maximum 12,000 (±500) r.p.m. Thelowest speed is normally around 6000 r.p.m. At the end of the test,cleanliness of various parts of the engine is measured. The results areshown in the table below. The maximum (best) rating for totalcleanliness is 15.

mounts, % by weight Ex 5* Ex 6* Ex 7* Ex 8* Ex 9 Mineral oil: Balance to= 100% Polyisobutene 30.6 30.6 30.6 30.6 30.6 Solvent 25.0 25.0 25.025.0 25.0 Polyolefin-substituted phenol 3.57 3.57 3.57 3.57 3.57Overbased Ca phenate 0.42 0.42 0.42 0.42 0.42 detergent Mannichdispersant^(c) — — — 1.00 0.43 Succinimide dispersant^(d) — 0.52 1.04 —0.37 Cleanliness ratings: Crankcase 3.00 3.00 3.50 3.00 3.75 Pistonskirt 2.50 3.00 3.00 3.00 3.00 Ring area 3.25 3.25 3.50 3.00 3.50 Total8.75 9.25 10.00 9.00 10.25 *A reference or comparative example.^(c)product of polyisobutylene phenol, formaldehyde, and dimethylamine;includes 10-11% heavy aromatic solvent. ^(d)4.7% N content

The results show significantly improved overall cleanliness for theformulation of Example 9, even though the total amount of dispersants isconsiderably less than in comparative Examples 6-8.

Each of the documents referred to above is incorporated herein byreference. The mention of any document is not an admission that suchdocument qualifies as prior art or constitutes the general knowledge ofthe skilled person in any jurisdiction. Except in the Examples, or whereotherwise explicitly indicated, all numerical quantities in thisdescription specifying amounts of materials, reaction conditions,molecular weights, number of carbon atoms, and the like, are to beunderstood as modified by the word “about.” It is to be understood thatthe upper and lower amount, range, and ratio limits set forth herein maybe independently combined. Similarly, the ranges and amounts for eachelement of the invention can be used together with ranges or amounts forany of the other elements. As used herein, the expression “consistingessentially of” permits the inclusion of substances that do notmaterially affect the basic and novel characteristics of the compositionunder consideration.

1. A lubricant composition comprising: (a) an oil of lubricatingviscosity; (b) about 0.1 to about 2 percent by weight of an ashlessMannich dispersant; (c) about 0.1 to about 2 percent by weight of anashless succinimide dispersant; and (d) a metal-containing detergent inan amount to deliver about 0.01 to about 0.12 percent sulfated ash tothe lubricant composition. wherein the succinimide dispersant providesat least about 40 parts per million by weight of nitrogen atoms to thelubricant composition.
 2. (canceled)
 3. The lubricant composition ofclaim 1 wherein the Mannich dispersant comprises the reaction product ofa polyisobutene-substituted phenol, formaldehyde or a reactiveequivalent of formaldehyde, and dimethylamine.
 4. The lubricantcomposition of claim 1 wherein the amount of the Mannich dispersant isabout 0.2 to about 1.05 percent by weight.
 5. The lubricant compositionof claim 1 wherein the succinimide dispersant is a condensation productof hydrocarbyl-substituted succinic anhydride or a reactive equivalentthereof, with a polyethylene polyamine.
 6. The lubricant composition ofclaim 1 wherein the succinimide dispersant has a total base number of atleast about 70 on an oil-free basis.
 7. The lubricant composition ofclaim 1 wherein the succinimide dispersant has a total base number of atleast about 90 on an oil-free basis.
 8. The lubricant composition ofclaim 1 wherein the succinimide dispersant has a nitrogen content of atleast about 3 percent by weight on an oil-free basis.
 9. The lubricantcomposition of claim 1 wherein the amount of the succinimide dispersantis about 0.2 to about 1 percent by weight.
 10. (canceled)
 11. Thelubricant composition of claim 1 wherein the weight ratio of the Mannichdispersant to the succinimide dispersant is about 80:20 to about 20:80.12. The lubricant composition of claim 1 wherein the metal-containingdetergent is an overbased sulfonate, phenate, salicylate, or salixaratedetergent.
 13. The lubricant composition of claim 1 wherein the metalcontaining detergent comprises an overbased calcium phenate detergent.14. The lubricant composition of claim 1 wherein the metal containingdetergent contributes at least about 0.1 total base number to thelubricant composition.
 15. The lubricant composition of claim 1 whereinthe amount of phosphorus contained therein is 0 to 0.05 weight percent.16. The lubricant composition of claim 15 wherein the amount ofphosphorus is provided by one or more zinc dialkyldithiophosphates. 17.A composition prepared by admixing the components of claim
 1. 18. Amethod of lubricating an internal combustion engine, comprisingsupplying thereto the lubricant composition of claim
 1. 19. The methodof claim 18 wherein the internal combustion engine is a two-stroke cycleengine.
 20. The method of claim 18 wherein the internal combustionengine has a power output of less than 150 kW (201 horsepower).
 21. Themethod of claim 18 wherein the internal combustion engine has a poweroutput of 0.1 to 15 kW.
 22. The method of claim 18 wherein the lubricantcomposition is provided as a mixture with a liquid fuel.